The Gemara in Megilla (7a) says the famous line “M’Chiyuv Inish L’Besume….. – One is obligated to drink on purim” Then straight away a story is told of Raba and Rav Zeira. they were at Seuda together, when suddenly Rava “Slaughters” Rav Zeira.
What is going on here why do we drink and why did Raba Kill Rav Zeira??
The aveira of the Yehudim was that they bowed down to Nevuchadnetzar’s idol. Even though it technically wasn’t Avodah Zara they should have been Moser Nefesh like Chanania, Mishael, and Azarya. Their tshuva was to serve Hashem untilthe point of dying Al Kiddush Hashem which they did after Haman’s decree was signed.
Similarly our avodah on Purim is to imagine ourselves willing to die Al Kiddush Hashem. The gemara says in Sanhedrin (43a) that when someone is sentenced to death by Bais Din, on their way to their execution they are given wine in order that they should be intoxicated and not feel pain. So too us since we are prepared to literally give up our lives we drink wine to ease our pain.
This explains why after getting drunk Raba slaughtered Rav Zeira. Since they both had in their minds that they were dying, Raba got a little carried away as the line between reality and fiction blurred to the point where he carried out his holy Kovanos and killed His friend al Kiddush Hashem. Thankfully He davened Hard enough and Boruch Hashem Rav Zeira came back to life!!
But this is the real reason we drink and we should all have this in mind before we open the wine on purim!!